In a July 10 letter, Hagel warns of the possibility that “draconian actions” may be needed to reduce personnel costs, including halting all accessions, freezing promotions, canceling all reassignments and terminating any discretionary bonuses.

For civilian workers, he warned of hiring freezes and involuntary reductions in force.

On readiness-related accounts, training and maintenance programs would continue at low levels and “in some cases” be cut even further, and weapons modernization accounts could be cut by 15 percent to 20 percent.

The warning comes in Hagel’s response to questions raised by the Senate Armed Services Committee about how to deal with a situation in which the Obama administration’s 2014 defense budget is $52 billion over the spending caps set in the 2011 Budget Control Act.

The White House and Congress have been planning the 2014 budget as if those caps would be removed, on the assumption that agreement would be reached on revenue, spending and deficit matters.

But such agreement remains elusive. The House, Senate and White House have approved their own separate plans but no negotiations are under way to reach a deal.

He said tough budget-cutting measures could be softened if Congress would go along with initiatives to reduce personnel costs. He specifically mentioned proposals to slow growth in military pay, raise health care fees for military retirees and eliminate restrictions that are slowing the rate of personnel reductions in the Army and Marine Corps.

“If Congress does not approve these proposals, even more cuts in combat power, readiness and modernization would be needed to accommodate cuts of $52 billion in fiscal year 2014 and similar cuts in later years,” Hagel says.